Peter A. Kulakow, Laura L. Benson, and Jake G. Vail

Illinois bundleflower [Desmanthus illinoensis (Michx.) MacM.] is a warm
season perennial legume of the North American grasslands. Native stands occur
in a variety of habitats, including rocky open ground, wooded slopes, prairies,
stream banks, roadsides, and along railroad rights-of-way In this paper, we
review the prospects for domesticating Illinois bundleflower as a perennial
seed crop and consider the species' nutritional value, nitrogen fixation
capacity, and potential for genetic improvement. In our efforts to achieve a
sustainable agriculture, we are using the native grasslands of the Great Plains
as a model for an agriculture based on domestication of herbaceous perennial
species as seed crops. These crops are selected for cultivation in
polycultures as contrasted with the extensive annual grain crop monocultures
typical of North American agriculture. These perennial crops would protect
soil from erosion and reduce traction power requirements, while the ecological
functioning of polycultures would help maintain soil fertility and control
pathogens, weeds, and phytophagous insects.

Illinois bundleflower is rated by some authorities as our most important native
legume and is included in range revegetation programs since the species is
readily eaten by livestock (Great Plains Flora Association 1986). The
lenticular seeds contain 38% protein on a dry weight basis, which compares
favorably with soybean [Glycine max (L.) Merr.] (Table 1). Chick
feeding trials and analyses of foliage and seed by the USDA Poisonous Plants
Research Laboratory found no toxic levels of oxalates, cyanides, nitrates or
alkaloids (M. Coburn Williams, pers. commun.).

Our long term objective is to use Illinois bundleflower to meet human
nutritional needs. Illinois bundleflower seed proteins are rich in
sulfur-containing amino acids and limiting in valine, isoleucine, tryptophan,
lysine, and threonine compared to the FAO standard reference protein (Table 2).
Additional analysis by the University of Nebraska Food Protein Research Group
found protein in uncooked seed to be 69% digestible with digestibility rising
to 80% and 83% after boiling seed for 30 and 60 minutes, respectively (Lowell
Satterlee, pers. commun.). Computed Protein Efficiency Ratios indicate that
while cooked Illinois bundleflower seed may be lower in protein quality than
soybeans or casein, it appears to be greater or equal to whole corn, wheat, and
cooked oats (Table 3). This preliminary information indicates that further
analysis of the nutritional quality of Illinois bundleflower is warranted. As
the seed leaves an unpleasant aftertaste studies are needed to determine the
cause of seed unpalatability. While the seed contains no detectable levels of
tannins (Larry Butler, pers. commun.), other chemical compounds may affect
flavor.

As part of a perennial mixed cropping system incorporating warm season and cool
season grasses, Illinois bundleflower could provide a harvest of nutritious
seed and enhance soil fertility through biological nitrogen fixation. The
percentage of nitrogen derived from symbiosis in perennial native legume
species is likely to be greater than that of annual grain legumes, as the
nodules are perennial and fixation may begin earlier than in annuals (Salisbury
and Ross 1985). Appreciable amounts of nitrogen transfer from perennial forage
legumes to grasses occurs in mixed swards (Brophy et al. 1987). This nitrogen
transfer from legume components could be a significant factor in maintaining
soil fertility of perennial polycultures. We screened 37 accessions of
Illinois bundleflower for nitrogen fixation as measured by acetylene reduction.
Seventy day old seedlings had an average activity per plant of 141 +/- 65
nmoles/min. These data are comparable to acetylene reduction rates found in
'Corsoy' soybean and alfalfa (Medicago sativa L.) (Lindemann et al.
1982, Duhigg et al. 1978). Significant variation among accessions in mean
acetylene reduction rate per plant, ranging from 40 to 302 nmoles/min, suggests
genetic variation in this trait which could be enhanced by a selection program.

Natural populations of Illinois bundleflower are distributed from North Dakota
and Minnesota in the north to New Mexico and Colorado in the west and from
Texas to Florida in the south (Great Plains Flora Association 1986). We have
assembled Illinois bundleflower germplasm collections from ten states and have
begun evaluating morphological and phenological variation for agronomic
potential. In 1987, 14 accessions were evaluated in a field nursery for 30
qualitative and quantitative descriptors to develop methods for describing
agronomic characteristics of Illinois bundleflower and to identify
characteristics that would be important for breeding cultivars (Mecko-Ray
1987). Means and ranges for eight phenological and yield related descriptors
are summarized in Table 4. Time of peak flowering was positively correlated
with 100 seed weight (r = 0.56, n = 14) but negatively correlated with seed
weight per plant (r = -0.57). Plant growth characteristics that seemed most
likely to affect agronomic performance included duration of flowering or
synchrony, presence of determinate vs. indeterminate branching patterns and a
tendency toward a prostrate vs. erect growth habit.

In 1988, we began a three-year field evaluation of 82 accessions transplanted
in a randomized complete block design with two replications. During the
establishment year, data was collected on plant height, vegetative vigor and
seed yield per plot. Analysis of variance showed significant differences among
accessions for all characteristics. Mean seed yield per accession was 1200
kg/ha with a range of 615 to 1700 kg/ha. Seed yield was correlated with both
vegetative vigor (r = 0.45, n = 80) and plant height (r = 0.50). The germplasm
represented ten states with most of the accessions from Kansas (n = 46) and
Oklahoma (n = 18). Sixteen of the 30 lowest yielding accessions were from
Oklahoma, with only one accession from Oklahoma yielding above the mean.
Kansas accessions averaged 1290 kg/ha while Oklahoma accessions averaged only
950 kg/ha. Accessions from Oklahoma also showed reduced vegetative vigor and
plant height. These observations provide evidence of latitudinal geographic
variation for adaptation to our central Kansas environment.

The most important variation observed in 1988 was resistance to seed shattering
in accession 391 from Knoxville, Tennessee. Illinois bundleflower seed pods
normally dehisce at maturity, which results in high seed shattering if harvest
is delayed after maturity. Accession 391 has indehiscent pods and is thus more
shatter resistant. Three naturally occurring hybrids between 391 and normal
dehiscent pod types have been identified and are being used to study the
inheritance of this form of shatter resistance (Fig. 1).

Successful development of Illinois bundleflower as a perennial grain legume
will require simultaneous progress in identifying uses for Illinois
bundleflower seed appropriate for its nutritional value and selecting
agronomically acceptable varieties. Perennial seed crops will most likely be
used on land prone to soil erosion where annual plowing is undesirable. Use of
Illinois bundleflower's nitrogen fixation potential could reduce nitrogen
fertilizer needs in perennial agroecosystems. Our initial breeding priorities
are focused on selection for harvestability, including resistance to seed
shattering and selection for stable high seed yields over multiple years.
Preliminary data on nutritional value, nitrogen fixation, seed yield, and
genetic variability in germplasm accessions suggest Illinois bundleflower has
promise as a perennial grain legume.